Diatoms of North AmericaDiatoms of North America

Pinnularia obscura

Krasske 1932

Pinnularia obscura guide
  • Category
    Symmetric Biraphid
  • Length Range
    19-36 µm
  • Width Range
    5-6.8 µm
  • Striae in 10 µm
    10-16

Identification

Pinnularia obscura LM7 Pinnularia obscura LM5 Pinnularia obscura LM6 Pinnularia obscura LM1 Pinnularia obscura LM2 Pinnularia obscura LM3 Pinnularia obscura LM4
View image metadata

Description

Valves are linear-lanceolate, with cuneiform apices. The raphe is filiform. Striae are somewhat radiate in the center and convergent at the apices. The proximal raphe pores are small and teardrop-shaped. The axial area is narrow and linear, with a large central area widened to fascia. 

Several morphotypes of Pinnularia obscura were recognized by Krammer (2000). Specimens found in material from Alaska collected by Patrick and Freese (1961) shown here correspond to Krammer's "morphotype".

Autecology

This taxon was reported from surveys in rivers of the US (EPA Western EMAP, USGS Regional Survey 2017). According to Krammer (2000), this taxon has a wide-spread distribution in nordic and alpine regions. It is found in mosses, wet rocks, and other aerophilic habitats.

Original Description

  • Author
    Krasske 1932
  • Length Range
    12-21 µm
  • Width
    3-4.5 µm
  • Striae in 10µm
    15

Original Images

Pinnularia obscura orig illus
Pinnularia obscura orig desc

Cite This Page

Leppik, S., Potapova, M. (2024). Pinnularia obscura. In Diatoms of North America. Retrieved June 20, 2025, from https://diatoms.org/species/62605/pinnularia-obscura

Responses

The 15 response plots show an environmental variable (x axis) against the relative abundance (y axis) of Pinnularia obscura from all the stream reaches where it was present. Note that the relative abundance scale is the same on each plot. Explanation of each environmental variable and units are as follows:

ELEVATION = stream reach elevation (meters)
STRAHLER = distribution plot of the Strahler Stream Order
SLOPE = stream reach gradient (degrees)
W1_HALL = an index that is a measure of streamside (riparian) human activity that ranges from 0 - 10, with a value of 0 indicating of minimal disturbance to a value of 10 indicating severe disturbance.
PHSTVL = pH measured in a sealed syringe sample (pH units)
log_COND = log concentration of specific conductivity (µS/cm)
log_PTL = log concentration of total phosphorus (µg/L)
log_NO3 = log concentration of nitrate (µeq/L)
log_DOC = log concentration of dissolved organic carbon (mg/L)
log_SIO2 = log concentration of silicon (mg/L)
log_NA = log concentration of sodium (µeq/L)
log_HCO3 = log concentration of the bicarbonate ion (µeq/L)
EMBED = percent of the stream substrate that is embedded by sand and fine sediment
log_TURBIDITY = log of turbidity, a measure of cloudiness of water, in nephelometric turbidity units (NTU).
DISTOT = an index of total human disturbance in the watershed that ranges from 1 - 100, with a value of 0 indicating of minimal disturbance to a value of 100 indicating severe disturbance.